VW Caddy ECU Memory Lock Prevents Code Clearing

I had nearly the same issue with my 2018 VW Transporter TSI last month. As someone with some experience in car electronics and basic repairs, I initially tried clearing the codes myself using a basic scan tool, but the ECU diagnostics kept showing persistent errors. The computer system was indicating active memory locks, very similar to your situation. After two failed attempts at clearing it myself, I took it to a workshop specializing in auto repair and VW electronics. Their diagnosis revealed an undervoltage condition in the vehicle electrical system, which was preventing the ECU from properly clearing stored codes. The fix involved a complete electrical system check, recalibration of the battery management system, and a specialized reset procedure. Total cost was 240€, but it completely resolved the issue. The persistent codes haven't returned since. To provide more specific guidance for your case, could you share: The exact error codes showing up, Whether your battery has been replaced recently, If you notice any electrical issues like dim lights or slow starter, What methods youve already tried for clearing the codes This information would help determine if youre dealing with the same underlying issue I encountered.

Latest service was at 38000km. Thanks for the detailed response. Codes are P0302 and P0304, which started appearing right after replacing the spark plugs. No battery issues, running strong and starter works perfectly. Our basic OBD reader shows the control unit is registering misfires, though the engine runs smoothly. Tried clearing the codes multiple times with both generic and VW-specific scan tools, but the ECU fault codes keep returning within 10-15 minutes of driving. The memory lock seems to be preventing any permanent clearing of the codes. The main concern is whether this persistent ECU diagnostics issue could indicate a deeper problem with the engine management system, rather than just a coding glitch.

Having faced this exact scenario on my 2018 VW Transporter TSI, those misfire codes after spark plug replacement are quite telling. The fault codes returning so quickly points to something beyond a simple memory lock issue. In my case, after the initial confusion with persistent control unit errors, it turned out the new spark plugs werent properly gapped. Even though the engine ran smoothly, the ECU diagnostics were picking up minor inconsistencies in combustion. The fault memory lock was actually protecting us from clearing legitimate error codes. Key findings from my experience: Double check spark plug gaps (should be exactly to spec), Verify plug coil connections are fully seated, Inspect coil pack connectors for any signs of damage, Check that the correct spark plug type was installed The smooth running engine despite the codes matches what I experienced. The modern ECU is sensitive enough to detect issues before they become noticeable in performance. Would suggest verifying these points before pursuing more complex auto repair solutions. If everything checks out, the next step would be testing the ignition coils, as they can sometimes be damaged during spark plug replacement.

Thanks for the input. Took the car back to the shop today and had them recheck everything. You were spot on, turns out two of the coil pack connectors weren't fully seated after the spark plug change. The automotive diagnostics showed the exact same pattern you mentioned. The technician removed and properly reseated all coil packs, performed a complete control unit reset, and monitored the active memory for about 30 minutes. No more fault codes appearing now. The ECU diagnostics are completely clear after a proper test drive. Best part, they didn't charge anything since it was related to the original spark plug service. Really appreciate the guidance about checking the coil connections. Saved me from potentially paying for unnecessary repairs and helped identify the actual issue. For anyone else seeing similar persistent fault codes after spark plug replacement, definitely check those coil pack connections first. The car electronics are pretty sensitive to even slightly loose connections these days.